Utilize ISO when adjusting exposure

[jdpdev]

Currently, automatic exposure adjustment only uses shutter to match the exposure. ISO adjustment can be used to expand the range of the adjustment, improve image quality, and minimize use of less useful shutter speeds.

Concerns:

• One stop of ISO is a big change, but smaller increments may not be as useful as small shutter increments
• Need to determine logic for deciding whether to change ISO
  • Configure a range of optimal shutter speeds?
• After adjusting ISO the direction of shutter movement may need to be reversed